Mechanism for stacking sheets



July 24, 1962 w. E. VELVEL 3,046,008

MECHANISM FOR STACKING SHEETS Filed April 5, 1960 2 Sheets-Sheet 1 FIG.

INVENTOR WILLIAM EDWARD VELVEL ATTORNEY July 24, 1962 w, VELVEL 3,046,008

MECHANISM FOR STACKING SHEETS Filed April 5, 1960 2 Sheets-Sheet 2 INVENTOR WILLIAM EDWARD VELVEL BY fym/ ATTORNEY h 7' rates atent Oflhce 3,046,008 Patented July 24, 1962 3,946,428 MECHANISM FOR STACKING SHEETS William Edward Velvel, Claymont, DeL, assignors to E. L du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Apr. 5, 1960, Ser. No. 20,105 Claims. (Cl. 2'71--63) This invention relates to a mechanism for stacking successive sheets of flexible material into piles. More particularly, it relates to such a mechanism wherein the sheets are stacked in alignment without injury to their surfaces or edges. Still more particularly, it relates to such a mechanism which delivers and stacks successive sheets of flexible photo-sensitive material with a rollover action.

Various mechanisms for stacking flexible sheets into piles or stacks are known. They are used mainly in printing machines but have found use in machines for stacking sheets of photographic film and paper. These sheet materials, due to their extreme sensitiveness to abrasive forces, kinking and pressure which result in undesirable image formation after exposure and development, etc., must be handled carefully and the prior art mechanisms have not always been satisfactory for such purposes. In the stacking of large sheets of photographic film and paper, the difficulties of stacking them without injury hecome pronounced. This is because such films tend to curl and the hydrophilic surfaces tend to cling to adjacent sheets.

An object of this invention is to provide a simple and dependable mechanism for stacking successive sheets of flexible material into an aligned pile of sheets. Another object is to provide such a mechanism for stacking successive sheets of damage-sensitive flexible material into a precisely aligned pile in a gentle but positive manner. Yet another object is to provide such a mechanism in which sheets of protective interleaving material can be stacked simultaneously in the same pile with the primary sheets. Still another object is to provide such a mechanism that will stack sheets with clinging surfaces which cannot be subsequently jogged into alignment if they are delivered to the stack out of alignment. A further object is to provide such a mechanism which will stack sheets possessing considerable up or down curl. A still further object is to provide a mechanism that can stack sheets which arrive at the stacking location at irregular intervals. A still further object is to provide such a mechanism which can be incorporated with a web inspecting, cutting, and sheet-assorting machine. Still further objects will be apparent from the following description of the invention.

The apparatus of this invention in its broader aspects is a mechanism for stacking successive sheets of flexible material into piles which comprises a lower row of spaced, continuous narrow carrier belts adapted to travel in a circuitous path and around a terminal rollover drum, an upper row of coacting spaced continuous holding belts adapted to travel in a circuitous path above the lower row of belts, said path extending at least about a sheet length beyond the terminal rollover drum, a sheet stacking platen located beneath the rollover drum and extending beyond the rollover drum and beneath the upper belts, means on the platen for guiding and positioning the leading end of the sheets in the desired stacking location and means for diverting the leading end of successive sheets around the drum in about the path of the lower belts until said end reaches the stacking location. The means for guiding and positioning the leading end of the sheet preferably comprises a row of spaced deflecting fingers and a row of stop blocks. The successive sheets of flexible material in general pass about one-half way around the drum with the lower belts, and the half-circumference of the drum is substantially less than the length of the sheets of flexible material.

The mechanism of this invention will be understood more readily from the following description when reference is made to the accompanying drawings wherein:

FIG. 1 is a schematic View in side elevation of the mechanism for stacking into aligned superposition on a platen successive sheets of material,

FIG. 2 is a plan view of the rollover drum and associated parts of the mechanism,

FIG. 3 is a side elevation of the rollover drum, pneumatic holding means and associated parts of the mechanism,

FIG. 4 is a side elevation of an alternative reverse rollover drum and associated parts of the mechanism, and

FIG. 5 is a side elevation (enlarged) of a part of the mechanism of FIG. 1 showing a switch and memory wheel and valve controlling means for operating the pneumatic holding means (shown in section).

Referring now to the drawings, wherein the reference numerals refer to the same parts throughout the several views, a web of sheet material W, e.g., photographic film from a suitable roll or other source (not shown) passes between feed rolls 1. Simultaneously, if desired, another web W of sheet material, e.g., interleaving protective paper from a roll or other source (not shown) passes under guide roller 2 upwardly into contact with web W and passes in surface contact therewith between feed rolls 3. The superposed webs then come into operative contact with rotary cutter 4 whereby they are cut into successive superposed sheets which for convenience will be designated as cut sheets 5. The cut sheets are fed onto the spaced endless, narrow lower carrier belts 6. These belts are supported by end guide rollers 7, segmented rollover drum 8, and intermediate guide roller 9. An additional guide roller 10 or a plurality of such guide rollers are used to guide th narrow belts in the prescribed path.

The web or webs are fed to the rotary cutter at a certain speed and the cut sheets drop onto the carrier belts 6 in a manner so that the successive cut sheets are spaced from each other by a gap constituting about 5% to 10% or more of the sheet length. The cut sheets are held in position on the carrier belt to the rollover drums by means of separate endless, narrow upper confining belts 11 which are disposed immediately above the carrier belts.

As shown in FIGS. 1, 3 and 5, the confining belts like the carrier belts travel in a circuitous path and the path is determined by end rollers 12 and 13 and intermediate guide rollers 14 and 15 placed a short distance above the path of the carrier belts. A deflecting roller 16 for the upper belt may be provided near segmented rollover drum 8 and is placed lower than the upper periphery of the drums so that the path of the upper belts immediately beyond the drums is at a substantial downward angle, e.g., about 25". Guide rollers 17, 18 and 19 serve to guide the confining belts to the end roller 12. The rollover drum segments are slightly wider than the belts and recessed, -i.e., at a much smaller diameter between segments than the periphery of said segments.

As the cut sheets approach the rollover drum in a horizontal position, in order to record the position of the leading edge of each sheet S the carrier belts preferably pass under spaced cylindrical rollers 20 and 21 which extend all the way across the belts. Between these rollers is a grooved roll 22 of lesser diameter than rollers 20 and 21 and having a plurality of spaced grooves (not shown in width) adapted to receive and interfit with the narrow belts. The upper belts, in passing under roller 20, over roll 22 and under roller 21 are deflected from their normal path to the rollover drum. The grooves in the roll 22 keep the upper belts in alignment with the opposed lower carrier belts.

As shown more clearlyin FIG. 5, short continuous auxiliary belts 23 are looped 180 around each of rollers Zll and 21. These auxiliary belts are narrower in width than the opposed belts and located centrally in the spaces between the belts. Also, they are narrower in width than the spaces. The purpose of the auxiliary belts is to hold the cut sheets against the lower belt as the upper belt is passed around roll 22. If desired, the auxiliary belts and rollers can be omitted.

Near one side of the stacking mechanism and between, for example, the first two pairs of carrier and confining belts, is a small rotatable contact wheel 24 which is journalled in the end of a pivoted spring-biased arm 25 of electrical microswitch 26. The purpose of this wheel and microswitch is to detect the position of the leading end of each of the oncoming sheets. Associated with the rollover drum and driven in synchronism therewith is a rotatable memory disc 27 having a. magnetically receptive surface. As the microswitch is actuated an electrical impulse is carried through a suitable conductor to amplifier 28 and the amplified impulse is carried through a suitable conductor to a recording head 2% adjacent the magnetically receptive surface whereby the impulse is recorded on said surface. Two pickup heads 30 and 31, and an eraser head 32, are arranged sequentially around the disc in its direction of rotation and in spaced relationship to each other. The pickup heads are connected by means of suitable circuits to a solenoid 33 which in turn is operatively connected to a valve 34 connected to a source of clean compressed and having an outlet which is connected to air-jet manifolds 35 and 36. These manifolds extend across the mechanism in straight line and consist of pipes closed at one end with suitable caps 37 and at the other end are connected to valve 34 by suitable pipes, tubing or conduits (not shown). The manifolds have a plurality of jet orifices 38 of small diameter which are spaced lengthwise to eject air between the belts so that air jets will impinge on the sheets and hold them against the lower belts as they pass around the rollover drum. The axes of the orifices in a given manifold are in a common plane.

Beneath the rollover drums is a sheet receiving platen 39 which has affixed to its upper surface by any suitable means, e.g., welding or machine screws (not shown), a row of spaced stop blocks 40. The latter are suitably placed beneath the rollover drum and a short distance backwards from the vertical diameter of the drums. 'I hese blocks have walls which are in alignment in a vertical plane extending across the platen. Between the stop blocks in the space between the lower belts are pivoted fingers 41, the free ends of which slant downwardly from the rounded-off front end. The pivot point is not shown :for purpose of simplicity but the fingers are adapted to swing upwardly and downwardly about the pivot point so that when the sheets are stacked the desired number, the fingers pivot downwardly under slight pressure and hold the sheets in aligned stacks until they are removed as a stack or bundle from the platen.

If desired, the p aten can be mounted on suitable rollers intenfitting with a suitable track (latter not shown) on the sidewalls 43 of frame 44 (see FIG. 1).

In FIG. 4 there is shown a modified rollover drum mechanism. The view is taken from the opposite side of the mechanism shown in FIG. 1 as evident from the direction of movement of the belts which hold the cut sheet in position. These belts first pass nearly 170 degrees around roller 42, the axis of which preferably, as shown, is in the same vertical plane as that of the lower rollover drum. The cut sheets passing around the drum are stacked on the platen with the opposite surface uppermost as compared with those stacked by the mechanism of FIGS. 1 and 3. In each of these mechanisms, the leading end of each cut sheet lies against the stop blocks and the free end feeds out in somewhat radial form as shown in dotted lines a, b, c and d by the constraining and carrying action of the upper belts until the trailing end falls free and the flat sheet or sheets are stacked in alignment and superposition on the platen.

The operation of the entire mechanism shown in FIGS. 13 and 5 will now be explained.

The cut sheet or superposed sheets which are deposited on the moving lower belts travel with the lower belts then meet and are held in position on the lower belts by means of the upper belts. As the sheet approaches the rollover drum, the leading end of the sheet is detected by means of the rotatable contact wheel. The impulse or signal produced by the associated microswitch is recorded on the magnetic memory disc. As the detected sheet continues toward the rollover drum, the recorded signal in the disc approaches a pick-up head. When the leading end of the sheet reaches the point on the rollover drum where the upper holding belt no longer holds the sheet against the lower belt, the recorded magnetic signal on the disc reaches the first pick-up head and the solenoid valve is energized to admit compressed air to the air jets. The jets of air from manifolds 35 and 36 hold the sheet in peripheral contact with the outer surface of the lower belts as they proceed around the rollover drum. When the leading end reaches the radial angle of about 175, it strikes the slanting undersurface of the fingers which starts the sheet to peel away from the belts and rollover drum. Further advance of the sheet causes progressively greater peel-off until the leading end strikes the stopblocks. At or about this point (a radial angle of about 205 to 215 of the rollover drum) the airjets in the manifold are turned ofi in response to the recorded signal being picked up by the second pickup head associated with the memory wheel. With the leading end of the sheet pressing against the stopblocks, continued infeed of the sheet by the action of the upper and lower belts causes the sheet to separate from the periphery of the lower belt through most of the semi-circular expanse from the point of departure of the two belts to the stopblocks. The sheet moves radially away from the rollover drum thus forming about a bend in the sheet between the upper and the lower planar portion of the sheet lying on the sheetreceiving platen (or on a previously stacked sheet) until the trailing end falls clear of the upper belt and onto said platen or sheet. The recorded signal on the memory disc passes the erasure head and the signal is erased, thus clearing the magnetic memory disc for the reception of a new signal from the next successive sheet.

It is important that the air jets be actuated in a precise timed relationship to the position of the leading end of the sheet because, if the jets are turned on too late, the sheet will not roll out smoothly but will slide out in an uncontrolled manner. If the jets turn on too soon, the trailing end of the next preceding sheet may be blown clear of the upper belt. Still other disadvantages of improper actuation will be apparent to those skilled in the art.

For slow speed operation of the mechanism (up to about 50 ft./min. sheet speed) a time-delay can be interposed in the circuit between the microswitch and the recording head, thus causing the signal or impulse to be recorded on the disc later than normally. For higher speed operation (e.g., substantially above 50 feet per minute) the time-delay circuit is automatically shunted out.

The novel mechanism of this invention may be modified by combining with it a film inspection station and an associated memory device so that after the sheets are cut defective sheets pass to a reject station rather than to the rollover stacker. Additionally, counting devices can be added and when the stacks reach a predetermined count the incoming sheets can be directed to a second or third rollover stacking mechanism associated with other s,ose,oos

platens so that the sheets can be directed to the new platen while a stack is being removed from the filled platen.

The mechanism is particularly adapted for stacking sheets of photographic film. Previous sheet stacking mechanisms were not suitable for this purpose. Photographic film of large size, due to its limpness and weight, will not stop in a precise location in more elementary stacking mechanisms but, upon hitting a stop, buckles and rebounds. Due to the inherent curl a trailing end of a preceding sheet may remain bowed up in the path of the sheet being delivered. Also, the smooth adherent surfaces of the sheets tend to make them cling together and resist realignment by patting them on the edges or vibrating and jogging the stack.

It is useful in stacking sheets of film or foil from 0.002 to 0.010 inch in thickness and varying in length from 8 to 30 or more inches, e.g., sheets of regenerated cellulose, paper, polyethylene, polyethylene terephthalate and aluminum.

An advantage of this invention is that it provides a simple and dependable mechanism for decelerating a moving sheet to a standstill while controlling the movement and stacking it and successive sheets in a stack with a desired degree of precision.

The rollover stacking mechanism of this invention provides positive control of the sheets at all times and tolerates some curl in the stacked sheets in either direction. The mechanism has relatively few moving parts and they are simple in form and dependable in operation.

Flexible sheets of various materials other than photographic film can 'be handled in like manner. Thus, the mechanism can be used in the printing industry where the gentle deceleration and precise placement of each sheet could eliminate jogging and stack realignment devices, and reduce the amount of back trimming where such practices are used.

Still other uses and advantages of the invention will be apparent from the above description to those skilled in the art.

I claim:

1. A mechanism for stacking successive sheets of flexible material into piles comprising a lower row of spaced continuous narrow carrier belts adapted to travel in -a circuitous path and around a terminal rollover drum, an upper row of spaced continuous narrow holding belts adapted to travel in a circuitous path above the lower row of belts and coact therewith to guide sheets of flexible material, said path extending at least about a sheet length beyond the terminal rollover drum, a sheet stacking platen located beneath the drum and extending beyond said drum and beneath the upper belts, means on the platen for guiding and positioning the leading end of the successive sheets in the desired stacking location and means for diverting the leading end of successive sheets around the rollover drum substantially in the path of the lower belts until said end reaches the stacking location.

2. A mechanism as defined in claim 1 wherein said means for diverting the end of the sheets is pneumatically actuated.

3. A mechanism as defined in claim 1 wherein said row of upper belts at a point beyond the terminal rollover drum is deflected to follow an angularly downward path and is then further deflected to follow a substantially horizontal path.

4. A mechanism as defined in claim 1 wherein the means for diverting and holding the leading end of the sheets consists of pneumatic jets, means for timing the action of the jets so that they are adapted to start as each sheet starts to pass around the rollover drum and to stop as the sheet reaches the stacking location.

5. A mechanism as defined in claim 1 wherein the means for diverting and holding the leading end of the sheets includes two transverse manifolds having a plurality of small orifices suitable for the egress of air jets arranged in straight rows.

6. A mechanism as defined in claim 1 associated with means for detecting the leading end of each sheet carried by the lower belts, a memory device for recording the detection signal operating in synchronism with the carrier belts, and means for activating and deactivating the penumatic means in synchronized response to the recorded signal.

7. A mechanism as defined in claim 1 wherein said drum has a half-circumference substantially less than the length of each successive sheet.

8. A mechanism as defined in claim 1 wherein said means for guiding and positioning the leading end of the sheets consists of spaced lateral deflecting fingers and stop blocks.

9. In a flexible sheet transporting mechanism having a lower row of spaced continuous narrow carrier belts adapted to travel in a circuitous path and an upper row of coacting spaced continuous narrow holding belts adapted to travel in a circuitous path above said lower row, the combination of a diverting roller for the upper belts whereby the upper belts are diverted from and then back to their normal path in coactive relationship, and a row of spaced auxiliary belts traveling in a short circuitous path adjacent the path of the carrier and holding belts and adapted to hold successive sheets against the lower carrier belts while the upper belts are diverted from their normal paths.

10. In a mechanism as set forth in claim 9 the combination characterized in that the upper belts are narrower than the lower belts and the auxiliary belts overlap adjacent carrier belts.

References Cited in the file of this patent UNITED STATES PATENTS 180,880 Hoe Aug. 8, 1876 269,184 CroWell Dec. 19, 1882 965,375 Dean July 26, 1910 991,002 Miehle May 2, 1911 1,838,200 Tomtlund Dec. 29, 1931 1,902,436 Joachim Mar. 21, 1933 2,381,430 Belluche Aug. 7, 1945 2,941,797 Buss June 21, 1960 

